A steam turbine is used for mechanical drive or the like and is provided with a turbine main body having a rotatably supported rotor. The rotor is rotationally driven by supplying steam as a working fluid to the turbine main body. The steam which is supplied to the turbine main body, or steam extracted from the turbine main body, flows in a steam flow path of the steam turbine. A steam valve is provided in the steam flow path. The flow rate of the steam which is supplied to the turbine main body can be adjusted by adjusting the degree to which the steam valve is opened.
Further, a steam stop valve having small flow rate adjustment and shut-off functions is provided in a steam valve front stream of a turbine inlet.
As such steam valve and steam stop valve, for example, a configuration as shown in PTL 1 is generally used. That is, the technique of PTL 1 has a link mechanism connected to a valve shaft, and a drive mechanism connected to the link mechanism.